What Is a Single-Pole Circuit Breaker?

Protection for Standard Light and Outlet Circuits

In home circuit-breaker panels, the standard protection for electrical circuits is provided by either single-pole or double-pole circuit breakers. They are a critical part of the electrical current distribution, providing a safe way to manage branch circuits from the circuit breaker panel.

Circuit breakers fit into the circuit breaker box, usually found in a utility space in your home. They provide a bridge between the main bus bars in the panel that deliver power into your home from the utility company, and the circuit wires that run through your home.

The circuit breakers are where the hot wires for each circuit are connected.

The Function of Circuit Breakers

These devices monitor the amount of current being drawn by appliances and lighting fixtures along the circuit, and "trip" to shut down the circuit whenever the load becomes high enough to overheat the wires. Further, circuit breakers trip whenever they sense a short circuit or ground-fault that can pose a potential hazard.

Circuit breakers also offer a convenient place to shut off current to a circuit in order to make repairs or replacements to any of the fixtures served by it. The switch on the front of the circuit breaker can easily be flicked off to render a circuit momentarily dead; and if the circuit breaker trips, restoring power is an easy matter of resetting the lever. Make sure, though, to address the overload or circuit problem that has caused the circuit breaker to trip in the first place.

The amperage rating of a circuit breaker is printed on the front of the breaker casing, and whenever a circuit load exceeds this amperage, the breaker will trip and shut off. This most commonly happens when too many appliances or other devices are plugged into outlets along the circuit. Most common culprits are appliances that heat (space heaters, toaster, hair dryers, etc.) or those that drive motors (vacuum cleaners, etc.).

Single-Pole vs. Double-Pole Circuit Breakers

Single-pole circuit breakers supply 120-volt power to circuits, while double-pole circuit breakers supply 240-volts. Most of the light fixtures and ordinary plug-in outlets in your home are served by single-pole 120-volt breakers, while heavy appliances and utilities, such as clothes dryers, whole-house central air conditioning, and electric ranges, are served by 240-volt double-pole breakers.

Single-pole breakers come in a wide range of amperage ratings, with 15, 20, and 30-amp circuit breakers being the most commonly used in most household installations.

The shape and look of circuit breakers vary depending on the manufacturer of the breaker box, but in general, a 120-volt breaker will have a narrower profile than a 240-volt breaker that occupies two slots in the breaker box However, there are also "slim-line" breakers that allow you to squeeze in breakers for two circuits into a single slot, designed for use if your breaker box has no open slots.

Circuit breaker boxes are brand-specific when it comes to the breakers that may be used in them. That means, for example, that a single-pole breaker from a Square D circuit breaker panel should not be used in a General Electric panel.

They each have different specifications, tensions, and different mounting methods. Using a circuit breaker from another manufacturer is not safe and undoubtedly voids any warranties the company has for its equipment.

Single-pole breakers are the breakers that control virtually all the standard lighting in your home, and all outlets with standard two-slot outlet receptacles. Whenever a circuit trips and the lights and appliances along that circuit fall dark and quiet, it is a single-pole breaker you should inspect.

Whenever a circuit breaker trips, the lever on the front will snap to the opposite direction from its ON position. Some circuit breakers have a clear peep sight that shows red when the circuit breaker has tripped. This, along with the handle moving away from the ON position gives you a clear indication of which circuit is experiencing trouble.

Resetting the breaker is a simple matter of flipping the front lever back to the ON position. But unless you have reduced the overload or fixed whatever other problem exists, the breaker may trip again very quickly.